98% of my search results online for "Drop in sound decoder for Atlas RS3" is MRC with a drop in decoder with speaker for the original/early 80's release Atlas RS 3's (I have (2). Also the less than glowing comments with MRC decoders. Then, too, are the sound decoders that require a separate sound bug which I assume means a speaker which if this is the case then a complete "drop in" sounds like the better option.
Being new to this but wanting to try my hand at an installation I'm asking the experts here for input as to a recommended drop in sound decoder with speaker affixed options.
Sorry to say an all in one decent sound decoder for your little alcos is not available. A better alternative is a board replacement with separate speaker is the best choice for sound and performance. Look to something like this from Loksound, Tsunami, and QSI solutions. http://www.esu.eu/en/products/loksound/loksound-select-direct/
All three manufactures have them and are very very good. You will have to order the sound set for the ALCO when ordering the decoder.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
MRC is the only one with the speaker on the decoder board. Any other decoder will be better simply because you can use a larger speaker and enclosure. The one on the MRC board is out of necessitry very small.
The 'circuit board' in those locos is nothing more than a piece of palstic with a coupel of wires clipped in which press against the motor leads. Any decoder in the 'Atlas/Athearn' form factor will fit, they all have notches that fit over the pegs that hold the factory piece of plastic in place. You will have to cut back the light pipes and affix individual LEDs for lighting.
For best results, one os the weights should be cut back to fit a speaker and enclosure. As an alternative, a smaller spoeaker and enclosure can go in the cab space, with some cutting.
I am a fan of Loksound, the Loksound Select Direct will drop in. They have the proper Alco 244 sounds, and in their horn collection they have the one I need for my railroad, which had the M3RT-1 horn.
The MRC RS-3 decoder is absolutely HORRIBLE sounding. I picked up one cheap, just to see if it was any good. Not worth it. Do the extra work and use a good decoder. I have 4 of those locos, and all will be getting Loksounds and the biggest speaker I can figure out how to fit without totally removing the weights.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
This is an older Atlas RS3 I installed a Tsunami decoder and 16mm X 32mm speaker in. The Loksound Select Direct board is the same physical design, The rear weight was cut down and used as a mounting block for the speaker ....
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Mark R. This is an older Atlas RS3 I installed a Tsunami decoder and 16mm X 32mm speaker in. The Loksound Select Direct board is the same physical design, The rear weight was cut down and used as a mounting block for the speaker .... Mark.
Thanks for the pic.....but from the shape of the weights it looks like my Atlas RS3 predates yours, where the (2) weights are pressed up inside the the ends of the upper body above the wheel sets which would require a very narrow rectangle shaped speaker that fits up inside the thin upper body. Guess I'll have to take a closer look at the shape of the weights in my RS3....
rrinker MRC is the only one with the speaker on the decoder board. Any other decoder will be better simply because you can use a larger speaker and enclosure. The one on the MRC board is out of necessitry very small. The 'circuit board' in those locos is nothing more than a piece of palstic with a coupel of wires clipped in which press against the motor leads. Any decoder in the 'Atlas/Athearn' form factor will fit, they all have notches that fit over the pegs that hold the factory piece of plastic in place. You will have to cut back the light pipes and affix individual LEDs for lighting. For best results, one os the weights should be cut back to fit a speaker and enclosure. As an alternative, a smaller spoeaker and enclosure can go in the cab space, with some cutting. I am a fan of Loksound, the Loksound Select Direct will drop in. They have the proper Alco 244 sounds, and in their horn collection they have the one I need for my railroad, which had the M3RT-1 horn. The MRC RS-3 decoder is absolutely HORRIBLE sounding. I picked up one cheap, just to see if it was any good. Not worth it. Do the extra work and use a good decoder. I have 4 of those locos, and all will be getting Loksounds and the biggest speaker I can figure out how to fit without totally removing the weights. --Randy
Thanks (again) Randy. Your last paragraph confirms most of the MRC comments I'd seen.
I'll check out the Loksound Select Direct drop in as you recommended with the Alco 244 sounds. As for the speaker placement, I did find a link showing the conversion to DCC with the RS3 Atlas version I have - even had suggested part numbers.....and I thought I'd saved the link in my favorites but didn't...and I haven't been able to find it again (but still searching trying different RS3 conversion wording)
Speaking of which, the speaker in the "how to" was rectangular and attached to the inside roof of the cab after modifying the plastic windows insert so it would fit, then required notching out the body to allow clearance when the cab was put back on the body.
The ends of the light pipe were cut off as you said and a "v" cut into one each of the two ends to glue the LED's in place. I'd greatly appreciate the part numbers for the Loksound drop in and the required lighting diodes.....and if a resistor is required with the diodes what size if you have the info for all.
Hi over50:
I'm over 50 too - way over 50 but I can still say I'm in my 50's, for now at least!
I think you will have to remove some of the weights to fit a decent speaker and enclosure. I'm not sure from your last post, but I suspect that you may have missed that point from Mark's post.
If you could show us some pictures you might get some good suggestions about how to fit the sound in. Its going to be tight whatever you use.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
hon30critter Hi over50: I'm over 50 too - way over 50 but I can still say I'm in my 50's, for now at least! I think you will have to remove some of the weights to fit a decent speaker and enclosure. I'm not sure from your last post, but I suspect that you may have missed that point from Mark's post. If you could show us some pictures you might get some good suggestions about how to fit the sound in. Its going to be tight whatever you use. Dave
This shows the steps for a DCC conversion for my RS3 version. Note the size/shape of the weights that press into each end of the body. With this method the speaker is mounted in the top of the cab so the only weight modification is for placement of the bulbs.....but my preference is LED's. Randy suggested the LokSound Direct drop in which has the required resisters for LED headlights. What I don't know is what size LokSound speaker and baffle plus LED's to buy at this point. For the speaker size, my first thought is trying to fit a quarter inside the cab for size and then measure it in mm to get an idea ....
And just to mention.....I'm 73.....but the user name wayover50 makes me feel better....(wink)....
The various early Atlas RS units are functionally identical. All made by Kato. On some of my RS-3's, the weights usually stay stuck inside the hoods when lifting it off the shell, on others they drop out easily. But all the weights are identical.
For speaker size - this is where a dial caliper comes in handy, to measure available space. Another trick is to use a small block of balso and sand/carve it to size, then measure it once you have the largets size that fits but still allows the shell to slip on properly.. Loksound has a huge selection of speakers, plus you aren't limited to just their speakers. In fact, if those are 8 ohm speakers, the Select can use the exact same one that you used.
rrinker The various early Atlas RS units are functionally identical. All made by Kato. On some of my RS-3's, the weights usually stay stuck inside the hoods when lifting it off the shell, on others they drop out easily. But all the weights are identical. For speaker size - this is where a dial caliper comes in handy, to measure available space. Another trick is to use a small block of balso and sand/carve it to size, then measure it once you have the largets size that fits but still allows the shell to slip on properly.. Loksound has a huge selection of speakers, plus you aren't limited to just their speakers. In fact, if those are 8 ohm speakers, the Select can use the exact same one that you used. --Randy
Just a few more questions please,
What are the specs I should look for when selecting the LED's, i.e., clear, or color, size, volt/amp rating, etc.,?
And once I have the sizing should I look for a speaker with or without a baffle?
Last, I have (2) Athearn GP9's of the same vintage that I'd like to keep/convert as well. Will the same type Loksound Direct drop in board work (and fit) in these?
Proper LEDs for an RS-3 would be golden-white color ones, not the glaring bluish-white of other white LEDs. I use Miniatronics Yelo-Glo ones in my locos. The Select Diect already had resistors for the LEDs so they can be connected right to the decoder.
Speaker size is usually given without the baffle. They will sound weak, low volume, and absolutel yno bass, without a baffle. You'll want to get one with a baffle. It's possible t make your own by using bits of palstic to build up a sealed chamber around the speaker using the shell as aprt of it, but usually easier to install a baffle made for the speaker.
Athearns of that vintage will be Blue Box locos. There is no circuit board, everything will have tio be ahrd wired. You'll also want to test the motor current. The Loksound select can handle .75 amp continuius, the regular Loksound V4 can handle 1.1 amp. If the stall current is higher than this, you might want to look at remotoring.
Since there's no circuot board, you can do just about anything. If you cut down the tabs ont eh truck and solder wires on (repalce that huge metal clip cross the motor. This will leave a good amount of space above th gear towers for a speaker and enclosure. A small piece of sheet styrene can be glued over the motor to make a shelf to hold the decoder and wires up out of the way.
rrinker Proper LEDs for an RS-3 would be golden-white color ones, not the glaring bluish-white of other white LEDs. I use Miniatronics Yelo-Glo ones in my locos. The Select Diect already had resistors for the LEDs so they can be connected right to the decoder. Speaker size is usually given without the baffle. They will sound weak, low volume, and absolutel yno bass, without a baffle. You'll want to get one with a baffle. It's possible t make your own by using bits of palstic to build up a sealed chamber around the speaker using the shell as aprt of it, but usually easier to install a baffle made for the speaker. Athearns of that vintage will be Blue Box locos. There is no circuit board, everything will have tio be ahrd wired. You'll also want to test the motor current. The Loksound select can handle .75 amp continuius, the regular Loksound V4 can handle 1.1 amp. If the stall current is higher than this, you might want to look at remotoring. Since there's no circuot board, you can do just about anything. If you cut down the tabs ont eh truck and solder wires on (repalce that huge metal clip cross the motor. This will leave a good amount of space above th gear towers for a speaker and enclosure. A small piece of sheet styrene can be glued over the motor to make a shelf to hold the decoder and wires up out of the way. --Randy
Really appreciate the information and hand holding Randy. I'll go with the Miniatronics Yelo-Glo LED's you suggested and a baffle with the speaker. As for the Athearn GP9's, as best I can remember they were Blue Box ... which probably was like all Athearn diesel locos 30 years ago.
With my (2) Atlas RS3's the least hassle to convert the GP9's are going back in the packing box they were in when we moved to the condo. Given my age and the amount of new scenery build ahead of me both engines are now "will get to some day....or not" along with a copy of your last (2) paragraphs.
Again, thank you for the help!
Unless those GP9's are special for some reason, you might get more mileage out of sellign them off and picking up some Proto 2000 GP9s, which can be had with sound and DCC already installed. The Athearn ones are actually too wide (though tha tmeans a bigger speaker woudl fit) and aren't necessailry GP9's - there was some confusion back when that the loco was a GP7 without dynamics and if it had dynamics it was a GP9 - not true, but MR said it, Lionel used it in their ads, and so did Athearn.
Over50 Mark R. This is an older Atlas RS3 I installed a Tsunami decoder and 16mm X 32mm speaker in. The Loksound Select Direct board is the same physical design, The rear weight was cut down and used as a mounting block for the speaker .... Mark. Thanks for the pic.....but from the shape of the weights it looks like my Atlas RS3 predates yours, where the (2) weights are pressed up inside the the ends of the upper body above the wheel sets which would require a very narrow rectangle shaped speaker that fits up inside the thin upper body. Guess I'll have to take a closer look at the shape of the weights in my RS3....
I grind the sides of the weights down slightly so they are a loose fit in the shell. Yes, this is a later run than yours - on the ones like yours, I glue the weights to the chassis. Makes for a much easier installation with everything attached to the chassis. The 16mm X 32mm speaker and enclosure is a perfect slip fit into the RS3 shell.
rrinker Unless those GP9's are special for some reason, you might get more mileage out of sellign them off and picking up some Proto 2000 GP9s, which can be had with sound and DCC already installed. --Randy
Unless those GP9's are special for some reason, you might get more mileage out of sellign them off and picking up some Proto 2000 GP9s, which can be had with sound and DCC already installed.
Unfortunately it appears the Pennsylvania road name to maintain continuity with the (5) DCC engines I bought (and all of my coal cars and caboose's) isn't among the HO Proto GP9 DCC w/sound options. For now I'll have to stay with the "value" DCC only Bachmann GP9 I bought. After the fact I know but I bought the DCC lower tier/cost Bachmann's before I knew the right questions to ask about DCC and the cost to upgrade it with a good sound decoder and speaker would end up costing me close to $280 total spent....really not a cost effective move.
rrinker Proper LEDs for an RS-3 would be golden-white color ones, not the glaring bluish-white of other white LEDs. I use Miniatronics Yelo-Glo ones in my locos.
Proper LEDs for an RS-3 would be golden-white color ones, not the glaring bluish-white of other white LEDs. I use Miniatronics Yelo-Glo ones in my locos.
Randy....Do you have a product number for the LED color and mm size you used in your RS3's? I've been looking at the Miniatronics LED listing and if it's there I'm not seeing a "golden white" color option.
They're called "YeloGlo". They're on the white LED page. 3mm or 5mm either will work, the 5mm matches up closer to the light pipe.
What I did was cut the light pipe off behind the first set of pegs that hold it to the shell, near the ends of the hoods, and the polished the cut with fine sandpaper. I used heat shrink to hold the LED in contact with the end of the light pipe, but going forward i will drill shallow holes and then glue the LEDs in with Faller Xpert cement.
The light pipes kind of have to stay becasue the ends are not flat, they have protrusions that are the lenses for the light castings. If you totally remove the light pipes you would need some small lenses from MV and somehow mount the LED to the end wall so it shines out the lenses, just as easy to cut down the existing light pipes and use them.
rrinker They're called "YeloGlo". They're on the white LED page. 3mm or 5mm either will work, the 5mm matches up closer to the light pipe. What I did was cut the light pipe off behind the first set of pegs that hold it to the shell, near the ends of the hoods, and the polished the cut with fine sandpaper. I used heat shrink to hold the LED in contact with the end of the light pipe, but going forward i will drill shallow holes and then glue the LEDs in with Faller Xpert cement. The light pipes kind of have to stay becasue the ends are not flat, they have protrusions that are the lenses for the light castings. If you totally remove the light pipes you would need some small lenses from MV and somehow mount the LED to the end wall so it shines out the lenses, just as easy to cut down the existing light pipes and use them. --Randy
Gotcha. It helped, too, with a visit to my LHS earlier today...saw packages of both the 3mm and 5mm diameter YeloGlo LED's. Makes sense now having seen other packages labeled as "bright blue like daylight" or words to that effect. The 5mm looked a bit on the big side to me but you've been there and done that so that's what I'll buy.
And, yeah, I see what you mean with keeping the light pipes because of the lens protrusions that fit into the shell. From what I've read some guys have cut a "V" in the end of the trimmed light pipes and glued the LED's inside the "V". Not having done this before I don't know if just gluing the LED against the light pipe is ok or I should mount it such that the end of LED is at the bottom of the "V" facing forward.
Also, the more I've looked at the what's involved to mount a speaker I'm now leaning toward milling one of the weights to make room for a rectangle speaker and baffle. If I mount a round speaker and baffle to the cab roof I'll have to cut away the part of the body with the four notch holes that hold the cab in place to make room for it unless I'm missing something.
Well, the TSU AT1000 w/Alco 244 prime mover decoder install was successful including a test run .
Next I snipped each light pipe 3/8" back from the lens, filed elongated notches in each and glued in 3mm yellow glo LED's then wired them to the board. Then did a test run, so far so good.
Next I cut down one gear tower weight to mount a QSI 16mm x 32mm speaker and enclosure leaving just under 1/8th inch thickness then cut down the second gear tower weight for the stay alive cap. I Goo'ed the cap in place on one weight and then the speaker/enclosure to the other weight, then secured the weights to the frame mount. Did a test run and lights and sound checked out (caveat noted below)...
On a roll now, I taped the loose wiring to the decoder and motor housing leaving slack in the LED wiring for wiggle room to lay the body along side with the lenses glued into the body, tucked the LED wiring on top of the decoder while carefully sliding the body onto the frame and...........the speaker enclosure bottomed approximately 1/4 of an inch above the frame mount (and no doubt the LED leads which were pressed up against the top of the body).
I filed the gear tower weight "legs" to allow the weight to rest a hair's clearance above the gear tower and tried again. The speaker/enclosure still bottomed a tad over 1/8th inch from the frame mounting slots.
I removed the speaker and enclosure and even with it removed the wiring laying above the decoder - which was taped as close to the decoder as possible - came into play where I had to "work at" getting the body tabs to snap in place to the frame.
Bottom line....the 10mm height of the 16mm x 32mm speaker enclosure won't fit in the body of my Atlas RS3 even with the gear tower weight cut down to 1/16 inch clearance above the gear tower. And from your photo my mounted speaker height looked the same.
The only thing I can think of is the height of your speaker and enclosure has to be 5mm or under where my QSI combination is 10mm assuming the inside dimensions of your RS3 and mine are the same.
So...for me it's move to plan B, which is buying and mounting a TDS Mini Oval (and enclosure with overall dimension of 24mm L x 14mm W x 3.9mm H) to the inside of the cab roof (have to cut an opening in the body to allow for the speaker/enclosure mounted to the underside of the cab roof) and run the wires tot he decoder.
Heck of a learning experience .... and a pain in the rear thanks to my ignorance for tackling a first time decoder install in a 30 year old engine.
Oh, just to add, when I tested the decoder with everything wired I was getting a random static sound whether the engine was moving or sitting with the engine idling. I have no idea what could cause this....and even if I do get the smaller speaker mounted in the cab roof and wired and the body put back I'll be back with a new thread....
I used the same speaker enclosure as you .... the difference is the fact you are using the light tubes, and that is what is restricting the speaker from fulling fitting up into the shell.
I turn down 3mm LEDs so they fit right into the holes of the shell. This leaves only about 3/16" of LED protruding into the interior of the shell.
I prefer this way of lighting engine headlights. The original polished end of the LED makes a perfect lens for the headlight, and they are extremely bright (if you want them that way) unlike the light loss through a plastic tube.
Somethings's not in the right place if you have to force the body on even with the speaker removed - the decoder isn't that tall, and with the weight cut down there should be absolutely no clearance issues over the weight (with speaker removed). If it's close you can take a little more off the weight, and also gain a small fractio by sanding the bottom of the speaker enclosure. Sounds like there is trouble elsewhere though if it still needs to be jammed on with the speaker removed, it's interfering over the front weight, or else you have a LOT of excess wires. TCS has some tiny plugs you can use that would allow you to shorten the light wires yet still completely seperate the shell.
I agree with Randy - sounds like you have way too much excess wiring as well. The chassis in my picture is fully wired and operable. The only extra wires not shown are the three wires (white / yellow / blue) from the shell for the headlights to attach.
There is very little clearance inside the RS3 - you need to get a little creative to get those wires out of sight.
Another thing you may have missed .... make sure you've trimmed off any tabs or posts on the inside of the shell that may be interfering with things. Keep at it - you're almost there, just need some tweaking. You won't be as happy with that smaller speaker in the cab.
Lastly, make sure you seal the speaker itself to the enclosure. Those open goles in the corners need to be filled, it will really affect the sound if you don't. Silicone works great for this.
Mark R. I used the same speaker enclosure as you .... the difference is the fact you are using the light tubes, and that is what is restricting the speaker from fulling fitting up into the shell. I turn down 3mm LEDs so they fit right into the holes of the shell. This leaves only about 3/16" of LED protruding into the interior of the shell. I prefer this way of lighting engine headlights. The original polished end of the LED makes a perfect lens for the headlight, and they are extremely bright (if you want them that way) unlike the light loss through a plastic tube. Mark.
After I posted I reviewed your photo of the speaker mount and it hit me that none of the weight overhangs the gear tower, just the end of the enclosure. And it looks like the weight is shifted up against the decoder as well. I'll take another look and see what if any difference it would make for me. I'll also cut off all the original positioning stubs as you suggested.
I measured from the frame to the top of my speaker enclosure (with it mounted to the cut down weight over the gear tower) and compared it to the inside depth of the body. Major difference.....like, nearly 1/4 inch difference without any interference from the LED and leads mounted to the body.
The original light pipe is approximately 1/8" thick and was mounted flat to the body over the original board with the small lamp in the top center of the board. The Soundtraxx decoder snapped into the same holding tabs and but was slightly thicker accounting for the components. This means at best I have just under 1/8" clearance space for my 4 LED connecting wires with shrink tubing over the resistors and 2 speaker wires soldered to the board plus about 5 inches of folded slack in each LED wire pairs to give me some wiggle room taking the body on and off.
All said, with under 1/8" of open space above the Soundtraxx decoder for just the wiring alone I have the proverbial how to stuff 10lb of xxxxx into a 2lb bag problem.
As for the weights, I cut a shelf for the stay alive cap such that the cap rests even with the top of slot where the light pipe was but, again, it's clear the 3/8 stub with the lens bumps that I slotted and glued the LED to is hitting the end of the weight directly above it. I'll take a look at cutting the entire top of the weight instead of just the shelf for the cap and see if this helps with the interference.
And I'll also take a look at removing the weight over the gear tower entirely then shifting the speaker and weight up against the decoder. Maybe I can cut down the weight some more in this position such that it just clears the drive shaft coupling.
As for cutting down the LED's, it's been years since I used it but I have a 1970's vintage Unimat hobby lathe I bought from Penney's or Sears at the time (yes, Penney's back then sold a lot of hardware...) and (3) of the 3mm LED's left in the bag. I can't remember the last time I turned it on....
After all this if there's still a fit problem then it's on to plan B with the cab roof mounted mini oval speaker...
As I mentioned, there is really very little room in the RS3. On this particular RS3 my client wanted the hood fan to be opened up to "let the sound out" much to my disagreement. This opening was ultimately sealed back up from inside once he discovered the sound was indeed weaker with the open fan.
If you look closely, you can see the speaker under the grill - it's right up there very close to the hood ....
For the rear weight, it was cut down to the point when the rear truck was rocked upwards from the rear, it just touched the bottom of the speaker enclosure. It's a "just fit" to be sure. I'd still be surprised if you would be able to get the speaker up in there WITH the shortened light tube and LED in place, although it might just sneak in the end cavity if your speaker is snuggled up as tight as possible to the decoder.
One trick for avoiding the rats nest of wiring is to run your wiring under the decoder. Feed the wires up through the holes in the decoder and solder in place. Shorten each wire so you have just the length you need and not a bunch of extra you have to tie down somewhere.
Mark R. As I mentioned, there is really very little room in the RS3. On this particular RS3 my client wanted the hood fan to be opened up to "let the sound out" much to my disagreement. This opening was ultimately sealed back up from inside once he discovered the sound was indeed weaker with the open fan. If you look closely, you can see the speaker under the grill - it's right up there very close to the hood .... For the rear weight, it was cut down to the point when the rear truck was rocked upwards from the rear, it just touched the bottom of the speaker enclosure. It's a "just fit" to be sure. I'd still be surprised if you would be able to get the speaker up in there WITH the shortened light tube and LED in place, although it might just sneak in the end cavity if your speaker is snuggled up as tight as possible to the decoder. One trick for avoiding the rats nest of wiring is to run your wiring under the decoder. Feed the wires up through the holes in the decoder and solder in place. Shorten each wire so you have just the length you need and not a bunch of extra you have to tie down somewhere. Mark.
Mark... I just measured the depth of the hood again where the speaker sits atop the shortened weight - it's 23mm from the bottom of the hood to the center top of the hood - the maximum depth to work with. The frame to the top of the speaker enclosure mounted to the cut down weight - leaving only 1mm clearance above the gear tower - is 26mm. There's absolutely no way to find another 3mm and even if I could there'd be no room for even a turned down LED let alone wiring back to the board.
The only possible difference in your installation is the overall height of your 16mm x 32mm enclosure. The QSI enclosure I have measures 10mm top to bottom. I rounded the top long sides of the enclosure to try to conform to the curvature of the hood and what little I gained in depth was maybe a half mm - essentially no gain and still 3mm short of being able to snap the hood to the frame.
At this point short of finding a 16mm x 32mm speaker and enclosure that's 5mm overall in height - which would leave me 2mm for the wires to the LED above the speaker - my only alternative is the 14mm x 24mm mini oval and enclosure (from Tony's) mounted in the cab roof.
Edit...just checked Tony's and the enclosure for the 14mm x 24mm speaker is 1/4" O.A. height or 6.35mm plus 2mm thinner which might work mounted to the weight given it's shorter leaving possibly enough room for the LED and a couple of 28 or 30 gage wires back to the decoder.
Still can't understand why you can't make yours fit. (?)
I just measured the speaker / enclosure and mine measures 10.36mm total height. I did have to bevel the sides of the enclosure on the top edge to make it fit - it IS that tight. I also measured the interior (don't forget to include the thickness of the walkway in your calculations) and I get 26.26mm from the bottom of the walkway to the top center of the shell interior.
You did remove those two posts inside the shell that held the original light bar in place ? And you're sure it's not hitting your cut down light tube / LED ?
I'm not just guessing this "should" work - I KNOW it should work as I've done a few of them just like this.
Mark R. Still can't understand why you can't make yours fit. (?) I just measured the speaker / enclosure and mine measures 10.36mm total height. I did have to bevel the sides of the enclosure on the top edge to make it fit - it IS that tight. I also measured the interior (don't forget to include the thickness of the walkway in your calculations) and I get 26.26mm from the bottom of the walkway to the top center of the shell interior. You did remove those two posts inside the shell that held the original light bar in place ? And you're sure it's not hitting your cut down light tube / LED ? I'm not just guessing this "should" work - I KNOW it should work as I've done a few of them just like this. Mark.
And I wish it did fit Mark. As I wrote, the depth of the hood where the speaker is mounted is 23mm max measured from the bottom edge of the hood to the top center. I've cut the weight to where there's no more than a mm space above the gear tower and the measurement from the frame to the top of the enclosure is 26mm - there's just no way to squeeze a 26mm object into a 23mm space. And, yes I did cut off all the protruding stubs although there weren't any above the enclosure mount. I also sanded the bottom of the enclosure (gained maybe 1/2 mm) and beveled the long side top edges of it to help conforming to the shell curvature.
Looking at your photo again I noticed the flywheels on your engine are brass - mine are steel...and confirmed with a magnetized part grabber. And my motor enclosure looks different than yours including where the brass motor stub is located in your photo. At this point I've got to say it appears this isn't an apples to apples conversion scenario. This leaves the only conclusion being I indeed have an earlier model Atlas RS3 given the steel flywheels vs brass in yours plus what I can tell from the photo a different motor enclosure.
Regardless, and repeating, I've cut the weight all I can without crimping the gear housing movement, I sanded a 1/2 mm off the bottom of the speaker enclosure as well as beveled the long sides of it and even without the LED in place I still come up 3mm short of being able to snap the body into the frame. Without the speaker enclosure the body does snap in place - meaning the other end with the capacitor laying atop the cut down weight is not contributing to the fit problem.
I'm going to pick up a 14mm x 24mm mini oval with the 1/4" overall height enclosure this afternoon (assuming my LHS has them) and try again with mounting it to the weight. If this doesn't work then it's run this engine DCC only or mount the speaker/enclosure in the cab roof and be done with it.
You keep saying you are measuring the interior dimension from the bottom edge of the hood to top center. The shell sits ON the walkway assembly - are you taking into consideration the thickness of the walkway ? That raises the shell up that much more.
I've searched my files, but I can't find te reference right now - but somebody does make a thinner speaker enclosure for that speaker. I'm thinking it was Litchfield Station, but I don't know if they are still around or not - website doesn't work.
Another method I would suggest would be to scrap the enclosure and mount the speaker itself with the magnet against the top of the shell - wires can be routed on either side of the magnet. You need to seal the sides and ends of the speaker to the shell so the back of the speaker is air tight to the shell's interior.
Are we getting mixed up over which end is which? The long hood end - the one with the radiator fan opening - to me is the front since most roads ran them long hood forward. Some didn't. There's more space for the speaker under the long hood. I assume that's where everyone is trying to put the speaker, regardless if you call that the front or the back of the loco.
There should have been some plastic posts there which the original light bar clipped to. For my non-sound ones I just left them, in fact I only cut the light bar back to just inboard of those posts so the light bar is still held in place the same way. For a sound install, they definitely have to be removed and the light bars cut back much shorter, or else removed entirely and the lenses repalced. I'm not big on turning LEDs - it defintiely can be done, just do not disturb the fragile wire whisker inside that runs fromt he one lead to the top of the actual junction inside - hold a clear LED up to the light and you can see it in there. In fact I had an idea, which I might try. If the light bars are cut almost completely off, leaving just the lenses, some Microscale Crystal-Clear would hold the little remnet in place to act as a lense, and some surface mount LEDs attached behind it - Richmond Controls and others have the LEDs with wires already attached. Or since the lens holes re so small - Crystal Clear can actually form lenses and small windows by itself. Doesn;t seem that all that should be necessary though.